The first category is alloy permanent magnetic materials, including rare earth permanent magnetic materials (NdFeB Nd2Fe14B), samarium cobalt (SmCo), aluminum nickel cobalt (AlNiCo)
The second category is ferrite permanent magnetic materials (Ferrite)
According to different production processes, they can be divided into sintered ferrite, bonded ferrite and injection ferrite. These three processes can be divided into isotropic and anisotropic magnets according to different orientations of magnetic crystals.
These are the main permanent magnetic materials on the market, and some cannot be eliminated due to the original production process or cost, such as Cu Ni Fe, Fe Co Mo, Fe Co V, MnBi
Rare earth permanent magnetic material (Nd2Fe14B)
It can be divided into the following three types according to different production processes
Sintered NdFeB
(1) Sintered NdFeB - Sintered NdFeB permanent magnets are smelted after air flow milling, with high coercivity and extremely high magnetic properties. Its maximum magnetic energy product (BHmax) is more than 10 times higher than that of ferrite. Its mechanical properties are also quite good, and it can cut and process different shapes and drill holes. The highest working temperature of high-performance products can reach 200 ℃. Because its material content is easy to lead to corrosion, the surface must be coated differently according to different requirements. (such as zinc plating, nickel, environment-friendly zinc, environment-friendly nickel, nickel copper nickel, environment-friendly nickel copper nickel, etc.). It is very hard and brittle, has high anti demagnetization, high cost/performance ratio, and is not suitable for high working temperature (>200 ℃).
(2) Bonded NdFeB - Bonded NdFeB is a composite NdFeB permanent magnet made by evenly mixing NdFeB powder with adhesives such as resin, plastic or low melting point metal, and then using compression, extrusion or injection molding. The product can be directly made into various complex shapes without secondary processing. All directions of bonded NdFeB are magnetic and can be processed into NdFeB compression molds and injection molds. High precision, excellent magnetic properties, good corrosion resistance, good temperature stability.
(3) Injection molded neodymium iron boron (Zhusu NdFeB) - it has high accuracy and is easy to make thin-walled rings or thin magnets with complex anisotropic shapes
Sintered ferrite
The main raw materials of sintered ferrite include BaFe12O19 and SrFe12O19, which can be divided into isotropic and anisotropic magnets according to the different orientations of magnetic crystals. Because of its low price and moderate magnetic properties, it has become a widely used magnet. Ferrite magnets are made by ceramic process. They are also hard and brittle materials. Because of their good temperature resistance and low price, ferrite magnets have become widely used permanent magnets.
Rubber magnet
Rubber Magnet is one of the series of ferrite magnetic materials. It is a flexible, elastic and twisting magnet made by compounding bonded ferrite powder and synthetic rubber through extrusion molding, calendering molding, injection molding and other processes. It can be processed into strip, roll, sheet and various complex shapes. The rubber magnet consists of magnetic powder (SrO6Fe2O3), polyethylene (CPE) and other additives (EBSO, DOP), which are manufactured by extrusion and calendering. The rubber magnetic material can be of the same or different sex. It is made of ferrite magnetic powder, CPE and some trace elements, and can be bent, twisted and rolled. It can be used without more machining, and can also be shaped according to the required size. The rubber magnet can also be coated with PVC, back glue, UV oil, etc. according to customer requirements. Its magnetic energy product is between 0.60 and 1.50 MGOe. Application fields of rubber magnetic materials: refrigerators, information notice racks, fasteners that fix objects to metal bodies for advertising, etc., magnetic sheets for toys, teaching instruments, switches and sensors. It is mainly used in micro and special motors, refrigerators, disinfection cabinets, kitchen cabinets, toys, stationery, advertising and other industries.
Aluminium nickel cobalt
Aluminum nickel cobalt (AlNiCo) is the first permanent magnetic material developed, which is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. According to different production processes, it can be divided into sintered AlNiCo and cast AlNiCo. The products are mostly round and square in shape. The casting process can be processed into different sizes and shapes; Compared with the casting process, sintered products are limited to small sizes. The dimensional tolerance of the produced blanks is better than that of the casting products, and the magnetic properties are slightly lower than that of the casting products, but the machinability is better. Among the permanent magnet materials, the cast Al Ni Co permanent magnet has the lowest reversible temperature coefficient, and the working temperature can be as high as 600 ℃. Al Ni Co permanent magnet products are widely used in various instruments and other applications.
samarium cobalt
SmCo can be divided into SmCo5 and Sm2Co17 according to different compositions, which are the first generation and second generation rare earth permanent magnetic materials respectively. Its development is limited due to the scarcity and high price of raw materials. As the second generation rare earth permanent magnet, SmCo not only has a high magnetic energy product (14-28MGOe) and reliable coercive force, but also has good temperature characteristics in the rare earth permanent magnet series. Compared with NdFeB, SmCo is more suitable for working in high temperature environment (>200 ℃).
